The surface of the transfer roller immediately after the secondary image transfer onto the recording medium becomes close to a dried solid upon absorption by the liquid medium of a carrier liquid of the liquid toner contained in the primary transfer image. Consequently, residual toner on the surface of the transfer roller is adhered thereto in a dried state.
While the residual toner on the surface of the transfer roller is generally removed by scraping with a cleaning blade, the problem arises that with the residual toner being in the dried state, the cleaning blade is poor in removal rate and must also be high in durability. The problem also arises that toner entering micropores in the surface of the transfer roller is hard to remove.
Accordingly, a conventional cleaning device of this type for a transfer roller includes: downstream of a region on the surface of the transfer roller for image transfer onto a recording medium, a wiping roller adapted to rotate reversely to the transfer roller for rubbing the transfer roller; and a pair of cleaning blades, the wiping roller and the cleaning blades being disposed in order from the upstream side in the rotation direction of the transfer roller. The wiping roller is rotated while being supplied with a cleaning liquid to rub off the residual toner on the transfer roller surface together with the cleaning liquid whereafter the two cleaning blades act to clean the transfer roller surface (see JP 2007-11142 A).
In the conventional transfer roller cleaning device mentioned above, the wiping roll while being supplied with the cleaning liquid, is designed to rub the transfer roller surface. That is, residual toner on the transfer roller surface has a cleaning liquid applied at a position of the wiping roller. Consequently, as the speed of rotation of the transfer roller is increased, cleaning of the residual toner with the cleaning liquid tends to fail. It has thus been difficult to meet with high-speed printing with continuous paper.
In view of what is mentioned above, it is an object of the present invention to provide an electrophotographic printer provided with a transfer roller cleaning device which has a capability of meeting with high-speed printing requirement with continuous paper used as its recording medium and of minimizing residual toner on a transfer roller surface in high-speed production as well.